Speech synthesizer using artificial intelligence, method of operating speech synthesizer and computer-readable recording medium

ABSTRACT

A speech synthesizer using artificial intelligence includes a memory, a communication unit for receiving utterance information of words uttered by a user, and a processor for acquiring a plurality of utterance intonation phrase (IP) ratios respectively corresponding to a plurality of words uttered by the user based on the utterance information, acquiring a plurality of non-utterance IP ratios respectively corresponding to a plurality of unuttered words based on the utterance information and the plurality of utterance IP ratios, and generating a personalized synthesized speech model based on the plurality of utterance IP ratios and the plurality of non-utterance IP ratios. A plurality of classes indicating reading break of a word includes first to third classes. A minor class has a smallest count among the first to third classes. Each of the utterance and non-utterance IP ratios is a ratio in which a word is classified as the minor class.

TECHNICAL FIELD

The present invention relates to a speech synthesizer and, moreparticularly, to a speech synthesizer capable of improving reading breakprediction performance

BACKGROUND ART

Competition for speech recognition technology which has started insmartphones is expected to become fiercer in the home with diffusion ofthe Internet of things (IoT).

In particular, an artificial intelligence (AI) device capable of issuinga command using speech and having a talk is noteworthy.

A speech recognition service has a structure for selecting an optimalanswer to a user's question using a vast amount of database.

A speech search function refers to a method of converting input speechdata into text in a cloud server, analyzing the text and retransmittinga real-time search result to a device.

The cloud server has a computing capability capable of dividing a largenumber of words into speech data according to gender, age and intonationand storing and processing the speech data in real time.

As more speech data is accumulated, speech recognition will be accurate,thereby achieving human parity.

Recently, services for providing a synthesized speech in specificspeaker's voice using a synthesized speech model have appeared.

For reading break learning of the synthesized speech model, a trainingset including one sentence (training data) and labeling data forlabeling words configuring the sentence with reading break is required.

The reading break may be classified into first reading break, secondreading break greater than the first reading break and third readingbreak greater than the second reading break.

When data having imbalance such as the count of specific reading breakless than that of other reading break is used upon outputting thesynthesized speech of one sentence, performance of the synthesizedspeech model may deteriorate.

In addition, in an existing synthesized speech model, only a uniformlysynthesized speech in which words are read with break according to theutterance style of a specific voice actor without considering theutterance style of a user was provided. Therefore, sometimes, the usermay feel uncomfortable when listening to the synthesized speech.

DISCLOSURE Technical Problem

Another object of the present invention is to provide a speechsynthesizer capable of improving reading break prediction performanceusing artificial intelligence when a synthesized speech is output.

Another object of the present invention is to provide a speechsynthesizer capable of outputting a synthesized speech optimized for areading break style of a person using artificial intelligence.

Technical Solution

A speech synthesizer using artificial intelligence according to anembodiment of the present invention includes a memory, a communicationunit configured to receive utterance information of words uttered by auser from a terminal, and a processor configured to acquire a pluralityof utterance intonation phrase (IP) ratios respectively corresponding toa plurality of words uttered by the user based on the utteranceinformation, acquire a plurality of non-utterance IP ratios respectivelycorresponding to a plurality of unuttered words based on the utteranceinformation and the plurality of utterance IP ratios, and generate apersonalized synthesized speech model based on the plurality ofutterance IP ratios and the plurality of non-utterance IP ratios. Aplurality of classes indicating reading break of a word includes a firstclass corresponding to first reading break, a second class correspondingto second reading break greater than the first break and a third classcorresponding to third reading break greater than the second break,wherein a minor class has a smallest count among the first to thirdclasses, and each of the utterance IP ratios and the non-utterance IPratios is a ratio in which a word is classified as the minor class.

Advantageous Effects

According to the embodiment of the present invention, as performance ofa synthesized speech model is improved, it is possible to naturallyoutput a synthesized speech. Therefore, a listener may not feeluncomfortable when listening to the synthesized speech.

According to the embodiment of the present invention, as a personalizedsynthesized speech model is provided, a synthesized speech suiting theutterance style of a user is output, thereby improving user'ssatisfaction with a speech recognition service.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a terminal according to thepresent invention.

FIG. 2 is a diagram illustrating a speech system according to anembodiment of the present invention.

FIG. 2 is a view illustrating the concept of another example of adeformable mobile terminal according to the present invention.

FIG. 3 is a diagram illustrating a process of extracting utterancefeatures of a user from a speech signal according to an embodiment ofthe present invention.

FIG. 4 is a diagram illustrating an example of converting a speechsignal into a power spectrum according to an embodiment of the presentinvention.

FIG. 5 is a block diagram illustrating the configuration of a speechsynthesis server according to an embodiment of the present invention.

FIGS. 6 and 7 are views illustrating a class imbalance problem whenreading break is predicted through a conventional synthesized speech.

FIG. 8 is a flowchart illustrating a method of operating a speechsynthesis server according to an embodiment of the present invention.

FIG. 9 is a flowchart illustrating a process of performing dataaugmentation of a word based on prior information according to anembodiment of the present invention.

FIG. 10 is a view showing an IP frequency number and a non-IP frequencynumber of each word stored in a database according to an embodiment ofthe present invention.

FIG. 11 is a view illustrating an oversampling rate determined accordingto a ratio of a non-IP frequency number to an IP frequency number.

FIG. 12 is a ladder diagram illustrating a method of operating a systemaccording to an embodiment of the present invention.

FIG. 13 is a view illustrating a basic structure of a recurrent neuralnetwork.

FIG. 14 is a view illustrating a process of classifying wordsconfiguring a sentence into classes using a synthesized speech modelaccording to an embodiment of the present invention.

FIG. 15 is a flowchart illustrating a method of operating a speechsynthesis server using artificial intelligence according to anotherembodiment of the present invention.

FIG. 16 is a diagram illustrating prior information of each word storedin a database according to an embodiment of the present invention.

FIG. 17 is a diagram illustrating an example of a synthesized speechmodel according to an embodiment of the present invention.

FIGS. 18 to 21 are diagrams illustrating an example of correcting aclass classification probability set in consideration of an IP ratio anda non-IP ratio of a word according to an embodiment of the presentinvention.

FIG. 22 is a diagram illustrating a process of learning a synthesizedspeech model using a newly acquired second class classificationprobability set based on an IP ratio according to an embodiment of thepresent invention.

FIG. 23 is a ladder diagram illustrating a method of operating anothersystem of the present invention.

FIG. 24 is a view illustrating a plurality of IP tables respectivelycorresponding to a plurality of voice actors according to an embodimentof the present invention.

FIG. 25 is a view illustrating a normal IP ratio table according to anembodiment of the present invention.

FIG. 26 is a view illustrating a table including personalized IP ratiosand normal IP ratios of acquired words based on utterance information ofa user.

FIG. 27 is a view illustrating an IP ratio model according to anembodiment of the present invention.

FIG. 28 is a view illustrating a result of estimating personalized IPratios of words unuttered by a user according to an embodiment of thepresent invention.

FIG. 29 is a flowchart illustrating a process of updating a personalizedsynthesized speech model at a speech synthesizer according to anembodiment of the present invention.

BEST MODE

Description will now be given in detail according to exemplaryembodiments disclosed herein, with reference to the accompanyingdrawings. For the sake of brief description with reference to thedrawings, the same or equivalent components may be provided with thesame reference numbers, and description thereof will not be repeated. Ingeneral, a suffix such as “module” or “unit” may be used to refer toelements or components. Use of such a suffix herein is merely intendedto facilitate description of the specification, and the suffix itself isnot intended to have any special meaning or function. In the presentdisclosure, that which is well-known to one of ordinary skill in therelevant art has generally been omitted for the sake of brevity. Theaccompanying drawings are used to help easily understand varioustechnical features and it should be understood that the embodimentspresented herein are not limited by the accompanying drawings. As such,the present disclosure should be construed to extend to any alterations,equivalents and substitutes in addition to those which are particularlyset out in the accompanying drawings.

While ordinal numbers including ‘first’, ‘second’, etc. may be used todescribe various components, they are not intended to limit thecomponents. These expressions may be used to distinguish one componentfrom another component

When it is said that a component is ‘coupled with/to’ or ‘connected to’another component, it should be understood that the one component isconnected to the other component directly or through any other componentin between. On the other hand, when it is said that a component is‘directly connected to’ or ‘directly coupled to’ another component, itshould be understood that there is no other component between thecomponents.

The terminal described in this specification may include cellularphones, smart phones, laptop computers, digital broadcast terminals,personal digital assistants (PDAs), portable multimedia players (PMPs),navigators, portable computers (PCs), slate PCs, tablet PCs, ultrabooks, wearable devices (for example, smart watches, smart glasses, headmounted displays (HMDs)), and the like.

However, the artificial intelligence device 100 described in thisspecification is applicable to stationary terminals such as smart TVs,desktop computers or digital signages.

In addition, the terminal 100 according to the embodiment of the presentinvention is applicable to stationary or mobile robots.

In addition, the terminal 100 according to the embodiment of the presentinvention may perform the function of a speech agent. The speech agentmay be a program for recognizing the speech of a user and audiblyoutputting a response suitable to the recognized speech of the user.

The terminal 100 may include a wireless communication unit 110, an inputunit 120, a learning processor 130, a sensing unit 140, an output unit150, an interface 160, a memory 170, a processor 180 and a power supply190.

The wireless communication unit 110 may include at least one of abroadcast reception module 111, a mobile communication module 112, awireless Internet module 113, a short-range communication module 114 anda location information module 115.

The broadcast reception module 111 receives broadcast signals and/orbroadcast associated information from an external broadcast managementserver through a broadcast channel.

The mobile communication module 112 may transmit and/or receive wirelesssignals to and from at least one of a base station, an externalterminal, a server, and the like over a mobile communication networkestablished according to technical standards or communication methodsfor mobile communication (for example, Global System for MobileCommunication (GSM), Code Division Multi Access (CDMA), CDMA2000 (CodeDivision Multi Access 2000), EV-DO (Enhanced Voice-Data Optimized orEnhanced Voice-Data Only), Wideband CDMA (WCDMA), High Speed DownlinkPacket access (HSDPA), HSUPA (High Speed Uplink Packet Access), LongTerm Evolution (LTE) , LTE-A (Long Term Evolution-Advanced), and thelike).

The wireless Internet module 113 is configured to facilitate wirelessInternet access. This module may be installed inside or outside theterminal 100. The wireless Internet module 113 may transmit and/orreceive wireless signals via communication networks according towireless Internet technologies.

Examples of such wireless Internet access include Wireless LAN (WLAN),Wireless Fidelity (Wi-Fi), Wi-Fi Direct, Digital Living Network Alliance(DLNA), Wireless Broadband (WiBro), Worldwide Interoperability forMicrowave Access (WiMAX), High Speed Downlink Packet Access (HSDPA),HSUPA (High Speed Uplink Packet Access), Long Term Evolution (LTE),LTE-A (Long Term Evolution-Advanced), and the like.

The short-range communication module 114 is configured to facilitateshort-range communication and to support short-range communication usingat least one of Bluetooth™, Radio Frequency IDentification (RFID),Infrared Data Association (IrDA), Ultra-WideBand (UWB), ZigBee, NearField Communication (NFC), Wireless-Fidelity (Wi-Fi), Wi-Fi Direct,Wireless USB (Wireless Universal Serial Bus), and the like.

The location information module 115 is generally configured to acquirethe position (or the current position) of the mobile terminal.Representative examples thereof include a Global Position System (GPS)module or a Wi-Fi module. As one example, when the terminal uses a GPSmodule, the position of the mobile terminal may be acquired using asignal sent from a GPS satellite.

The input unit 120 may include a camera 121 for receiving a videosignal, a microphone 122 for receiving an audio signal, and a user inputunit 123 for receiving information from a user.

Voice data or image data collected by the input unit 120 may be analyzedand processed as a control command of the user.

The input unit 120 may receive video information (or signal), audioinformation (or signal), data or user input information. For receptionof video information, the terminal 100 may include one or a plurality ofcameras 121.

The camera 121 may process image frames of still images or moving imagesobtained by image sensors in a video call more or an image capture mode.The processed image frames can be displayed on the display 151 or storedin memory 170.

The microphone 122 processes an external acoustic signal into electricalaudio data. The processed audio data may be variously used according tofunction (application program) executed in the terminal 100. Meanwhile,the microphone 122 may include various noise removal algorithms toremove noise generated in the process of receiving the external acousticsignal.

The user input unit 123 receives information from a user. Wheninformation is received through the user input unit 123,

The processor 180 may control operation of the terminal 100 incorrespondence with the input information.

The user input unit 123 may include one or more of a mechanical inputelement (for example, a mechanical key, a button located on a frontand/or rear surface or a side surface of the terminal 100, a domeswitch, a jog wheel, a jog switch, and the like) or a touch inputelement. As one example, the touch input element may be a virtual key, asoft key or a visual key, which is displayed on a touchscreen throughsoftware processing, or a touch key located at a location other than thetouchscreen.

The learning processor 130 may be configured to receive, classify, storeand output information to be used for data mining, data analysis,intelligent decision, mechanical learning algorithms and techniques.

The learning processor 130 may include one or more memory unitsconfigured to store data received, detected, sensed, generated or outputin a predetermined manner or another manner by the terminal or received,detected, sensed, generated or output in a predetermined manner oranother manner by another component, device, terminal or device forcommunicating with the terminal.

The learning processor 130 may include a memory integrated with orimplemented in the terminal. In some embodiment, the learning processor130 may be implemented using the memory 170.

Selectively or additionally, the learning processor 130 may beimplemented using a memory related to the terminal, such as an externalmemory directly coupled to the terminal or a memory maintained in aserver communicating with the terminal.

In another embodiment, the learning processor 130 may be implementedusing a memory maintained in a cloud computing environment or anotherremote memory accessible by the terminal through the same communicationscheme as a network.

The learning processor 130 may be configured to store data in one ormore databases in order to identify, index, categorize, manipulate,store, retrieve and output data to be used for supervised orunsupervised learning, data mining, predictive analysis or othermachines.

Information stored in the learning processor 130 may be used by one ormore other controllers of the terminal or the processor 180 using anyone of different types of data analysis algorithms and machine learningalgorithms

Examples of such algorithms include k-nearest neighbor systems, fuzzylogic (e.g., possibility theory), neural networks, Boltzmann machines,vector quantization, pulse neural networks, support vector machines,maximum margin classifiers, hill climbing, inductive logic systemBayesian networks, Petri Nets (e.g., finite state machines, Mealymachines or Moore finite state machines), classifier trees (e.g.,perceptron trees, support vector trees, Marcov trees, decision treeforests, random forests), betting models and systems, artificial fusion,sensor fusion, image fusion, reinforcement learning, augmented reality,pattern recognition, and automated planning.

The processor 180 may make a decision using data analysis and machinelearning algorithms and determine or predict at least one executableoperation of the terminal based on the generated information. To thisend, the processor 180 may request, retrieve, receive or use the data ofthe processor 130 and control the terminal to execute preferableoperation or predicted operation of at least one executable operation.

The processor 180 may perform various functions for implementingintelligent emulation (that is, a knowledge based system, an inferencesystem and a knowledge acquisition system). This is applicable tovarious types of systems (e.g., a fussy logic system) including anadaptive system, a machine learning system, an artificial neural system,etc.

The processor 180 may include a sub module for enabling operationinvolving speech and natural language speech processing, such as an I/Oprocessing module, an environmental condition module, speech-to-text(STT) processing module, a natural language processing module, aworkflow processing module and a service processing module.

Each of such sub modules may have an access to one or more systems ordata and models at the terminal or a subset or superset thereof. Inaddition, each of the sub modules may provide various functionsincluding vocabulary index, user data, a workflow model, a service modeland an automatic speech recognition (ASR) system.

In another embodiment, the other aspects of the processor 180 or theterminal may be implemented through the above-described sub modules,systems or data and models.

In some embodiments, based on the data of the learning processor 130,the processor 180 may be configured to detect and sense requirementsbased on the context condition or user's intention expressed in userinput or natural language input.

The processor 180 may actively derive and acquire information necessaryto fully determine the requirements based on the context condition oruser's intention. For example, the processor 180 may actively deriveinformation necessary to determine the requirements, by analyzinghistorical data including historical input and output, pattern matching,unambiguous words, and input intention, etc.

The processor 180 may determine a task flow for executing a function forresponding to the requirements based on the context condition or theuser's intention.

The processor 180 may be configured to collect, sense, extract, detectand/or receive signals or data used for data analysis and machinelearning operations through one or more sensing components at theterminal, in order to collect information for processing and storagefrom the learning processor 130.

Information collection may include sensing information through a sensor,extracting information stored in the memory 170, or receivinginformation from another terminal, an entity or an external storagedevice through a communication unit.

The processor 180 may collect and store usage history information fromthe terminal.

The processor 180 may determine the best match for executing a specificfunction using the stored usage history information and predictivemodeling.

The processor 180 may receive or sense surrounding environmentinformation or other information through the sensing unit 140.

The processor 180 may receive broadcast signals and/or broadcast relatedinformation, wireless signals or wireless data through the wirelesscommunication unit 110.

The processor 180 may receive image information (or signalscorresponding thereto), audio signal (or signals corresponding thereto),data or user input information from the input unit 120.

The processor 180 may collect information in real time, process orclassify the information (e.g., a knowledge graph, a command policy, apersonalization database, a dialog engine, etc.), and store theprocessed information in the memory 170 or the learning processor 130.

When the operation of the terminal is determined based on data analysisand machine learning algorithms and techniques, the processor 180 maycontrol the components of the terminal in order to execute thedetermined operation. The processor 180 may control the terminalaccording to a control command and perform the determined operation.

When the specific operation is performed, the processor 180 may analyzehistorical information indicating execution of the specific operationthrough data analysis and machine learning algorithms and techniques andupdate previously learned information based on the analyzed information.

Accordingly, the processor 180 may improve accuracy of futureperformance of data analysis and machine learning algorithms andtechniques based on the updated information, along with the learningprocessor 130.

The sensing unit 140 may include one or more sensors configured to senseinternal information of the mobile terminal, the surrounding environmentof the mobile terminal, user information, and the like.

For example, the sensing unit 140 may include at least one of aproximity sensor 141, an illumination sensor 142, a touch sensor, anacceleration sensor, a magnetic sensor, a G-sensor, a gyroscope sensor,a motion sensor, an RGB sensor, an infrared (IR) sensor, a finger scansensor, an ultrasonic sensor, an optical sensor (for example, a camera121), a microphone 122, a battery gauge, an environment sensor (forexample, a barometer, a hygrometer, a thermometer, a radiation detectionsensor, a thermal sensor, and a gas sensor), and a chemical sensor (forexample, an electronic nose, a health care sensor, a biometric sensor,and the like). The mobile terminal disclosed in this specification maybe configured to combine and utilize information obtained from at leasttwo sensors of such sensors.

The output unit 150 is typically configured to output various types ofinformation, such as audio, video, tactile output, and the like. Theoutput unit 150 may include a display 151, an audio output module 152, ahaptic module 153, and a light output unit 154.

The display 151 is generally configured to display (output) informationprocessed in the terminal 100. For example, the display 151 may displayexecution screen information of an application program executed by theterminal 100 or user interface (UI) and graphical user interface (GUI)information according to the executed screen information.

The display 151 may have an inter-layered structure or an integratedstructure with a touch sensor in order to realize a touchscreen. Thetouchscreen may provide an output interface between the terminal 100 anda user, as well as function as the user input unit 123 which provides aninput interface between the terminal 100 and the user.

The audio output module 152 is generally configured to output audio datareceived from the wireless communication unit 110 or stored in thememory 170 in a call signal reception mode, a call mode, a record mode,a speech recognition mode, a broadcast reception mode, and the like.

The audio output module 152 may also include a receiver, a speaker, abuzzer, or the like.

A haptic module 153 can be configured to generate various tactileeffects that a user feels. A typical example of a tactile effectgenerated by the haptic module 153 is vibration.

A light output unit 154 may output a signal for indicating eventgeneration using light of a light source of the terminal 100. Examplesof events generated in the terminal 100 may include message reception,call signal reception, a missed call, an alarm, a schedule notice, emailreception, information reception through an application, and the like.

The interface 160 serves as an interface with external devices to beconnected with the terminal 100. The interface 160 may include wired orwireless headset ports, external power supply ports, wired or wirelessdata ports, memory card ports, ports for connecting a device having anidentification module, audio input/output (I/O) ports, video I/O ports,earphone ports, or the like. The terminal 100 may perform appropriatecontrol related to the connected external device in correspondence withconnection of the external device to the interface 160.

The identification module may be a chip that stores a variety ofinformation for granting use authority of the terminal 100 and mayinclude a user identity module (UIM), a subscriber identity module(SIM), a universal subscriber identity module (USIM), and the like. Inaddition, the device having the identification module (also referred toherein as an “identifying device”) may take the form of a smart card.Accordingly, the identifying device can be connected with the terminal100 via the interface 160.

The memory 170 stores data supporting various functions of the terminal100.

The memory 170 may store a plurality of application programs orapplications executed in the terminal 100, data and commands foroperation of the terminal 100, and data for operation of the learningprocessor 130 (e.g., at least one piece of algorithm information formachine learning).

The processor 180 generally controls overall operation of the terminal100, in addition to operation related to the application program. Theprocessor 180 may process signals, data, information, etc. input oroutput through the above-described components or execute the applicationprogram stored in the memory 170, thereby processing or providingappropriate information or functions to the user.

In addition, the processor 180 may control at least some of thecomponents described with reference to FIG. 1 in order to execute theapplication program stored in the memory 170. Further, the processor 180may operate a combination of at least two of the components included inthe terminal 100, in order to execute the application program.

The power supply 190 receives external power or internal power andsupplies the appropriate power required to operate respective componentsincluded in the terminal 100, under control of the controller 180. Thepower supply 190 may include a battery, and the battery may be abuilt-in or rechargeable battery.

Meanwhile, as described above, the processor 180 controls operationrelated to the application program and overall operation of the terminal100. For example, the processor 180 may execute or release a lockfunction for limiting input of a control command of the user toapplications when the state of the mobile terminal satisfies a setcondition.

FIG. 2 is a diagram illustrating a speech system according to anembodiment of the present invention.

Referring to FIG. 2, the speech system 1 includes an terminal 100, aspeech-to-text (STT) server 10, a natural language processing (NLP)server 20 and a speech synthesis server 30.

The terminal 100 may transmit speech data to the STT server 10.

The STT server 10 may convert the speech data received from the terminal100 into text data.

The STT server 10 may increase accuracy of speech-text conversion usinga language model.

The language model may mean a model capable of calculating a probabilityof a sentence or a probability of outputting a next word is output whenprevious words are given.

For example, the language model may include probabilistic languagemodels such as a unigram model, a bigram model, an N-gram model, etc.

The unigram model refers to a model that assumes that use of all wordsis completely independent of each other and calculates the probabilityof a word string by a product of the probabilities of words.

The bigram model refers to a model that assumes that use of wordsdepends on only one previous word.

The N-gram model refers to a model that assumes that use of wordsdepends on (n-1) previous words.

That is, the STT server 10 may determine when the speech data isappropriately converted into the text data using the language model,thereby increasing accuracy of conversion into the text data.

The NLP server 20 may receive the text data from the STT server 10. TheNLP server 20 may analyze the intention of the text data based on thereceived text data.

The NLP server 20 may transmit intention analysis information indicatingthe result of performing intention analysis to the terminal 100.

The NLP server 20 may sequentially perform a morpheme analysis step, asyntax analysis step, a speech-act analysis step, a dialog processingstep with respect to text data, thereby generating intention analysisinformation.

The morpheme analysis step refers to a step of classifying the text datacorresponding to the speech uttered by the user into morphemes as asmallest unit having a meaning and determining the part of speech ofeach of the classified morphemes.

The syntax analysis step refers to a step of classifying the text datainto a noun phrase, a verb phrase, an adjective phrase, etc. using theresult of the morpheme analysis step and determines a relation betweenthe classified phrases.

Through the syntax analysis step, the subject, object and modifier ofthe speech uttered by the user may be determined.

The speech-act analysis step refers to a step of analyzing the intentionof the speech uttered by the user using the result of the syntaxanalysis step. Specifically, the speech-act step refers to a step ofdetermining the intention of a sentence such as whether the user asks aquestion, makes a request, or expresses simple emotion.

The dialog processing step refers to a step of determining whether toanswer the user's utterance, respond to the user's utterance or questionabout more information.

The NLP server 20 may generate intention analysis information includingat least one of the answer to, a response to, or a question about moreinformation on the intention of the user's utterance, after the dialogprocessing step.

Meanwhile, the NLP server 20 may receive the text data from the terminal100. For example, when the terminal 100 supports the speech-to-textconversion function, the terminal 100 may convert the speech data intothe text data and transmit the converted text data to the NLP server 20.

The speech synthesis server 30 may synthesize prestored speech data togenerate a synthesized speech.

The speech synthesis server 30 may record the speech of the userselected as a model and divide the recorded speech into syllables orwords. The speech synthesis server 30 may store the divided speech in aninternal or external database in syllable or word units.

The speech synthesis server 30 may retrieve syllables or wordscorresponding to the given text data from the database and synthesizethe retrieved syllables or words, thereby generating the synthesizedspeech.

The speech synthesis server 30 may store a plurality of speech languagegroups respectively corresponding to a plurality of languages.

For example, the speech synthesis server 30 may include a first speechlanguage group recorded in Korean and a second speech language grouprecorded in English.

The speech synthesis server 30 may translate text data of a firstlanguage into text of a second language and generate a synthesizedspeech corresponding to the translated text of the second language usingthe second speech language group.

The speech synthesis server 30 may transmit the synthesized speech tothe terminal 100.

The speech synthesis server 30 may receive the intention analysisinformation from the NLP server 20.

The speech synthesis server 30 may generate the synthesized speechincluding the intention of the user based on the intention analysisinformation.

In one embodiment, the STT server 10, the NLP server 20 and the speechsynthesis server 30 may be implemented as one server.

The respective functions of the STT server 10, the NLP server 20 and thespeech synthesis server 30 may also be performed in the terminal 100. Tothis end, the terminal 100 may include a plurality of processors.

FIG. 3 is a diagram illustrating a process of extracting utterancefeatures of a user from a speech signal according to an embodiment ofthe present invention.

The terminal 100 shown in FIG. 1 may further include an audio processor181.

The audio processor 181 may be implemented as a chip separated from theprocessor 180 or a chip included in the processor 180.

The audio processor 181 may remove noise from the speech signal.

The audio processor 181 may convert the speech signal into text data. Tothis end, the audio processor 181 may include an STT engine.

The audio processor 181 may recognize a wake-up word for activatingspeech recognition of the terminal 100. The audio processor 181 mayconvert the wake-up word received through the microphone 121 into textdata and determine that the wake-up word is recognized when theconverted text data corresponds to the prestored wake-up word.

The audio processor 181 may convert the speech signal, from which noiseis removed, into a power spectrum.

The power spectrum may be a parameter indicating a frequency componentincluded in the waveform of the speech signal varying with time, and amagnitude thereof.

The power spectrum shows a distribution of an amplitude squared valueaccording to the frequency of the waveform of the speech signal.

This will be described with reference to FIG. 4.

FIG. 4 is a diagram illustrating an example of converting a speechsignal into a power spectrum according to an embodiment of the presentinvention.

Referring to FIG. 4, the speech signal 410 is shown. The speech signal410 may be received through the microphone 121 or prestored in thememory 170.

The x-axis of the speech signal 410 denotes a time and the y-axisdenotes an amplitude.

The audio processor 181 may convert the speech signal 410, the x-axis ofwhich is a time axis, into a power spectrum 430, the x-axis of which isa frequency axis.

The audio processor 181 may convert the speech signal 410 into the powerspectrum 430 using Fast Fourier transform (FFT).

The x-axis of the power spectrum 430 denotes a frequency and the y-axisof the power spectrum 430 denotes a squared value of an amplitude.

FIG. 3 will be described again.

The processor 180 may determine utterance features of a user using atleast one of the power spectrum 430 or the text data received from theaudio processor 181.

The utterance features of the user may include the gender of the user,the pitch of the user, the tone of the user, the topic uttered by theuser, the utterance speed of the user, the volume of the user's voice,etc.

The processor 180 may acquire the frequency of the speech signal 410 andthe amplitude corresponding to the frequency using the power spectrum430.

The processor 180 may determine the gender of the user who utters aspeech, using the frequency band of the power spectrum 430.

For example, the processor 180 may determine the gender of the user as amale when the frequency band of the power spectrum 430 is within apredetermined first frequency band range.

The processor 180 may determine the gender of the user as a female whenthe frequency band of the power spectrum 430 is within a predeterminedsecond frequency band range. Here, the second frequency band range maybe larger than the first frequency band range.

The processor 180 may determine the pitch of the speech using thefrequency band of the power spectrum 430.

For example, the processor 180 may determine the pitch of the speechaccording to the amplitude within a specific frequency band range.

The processor 180 may determine the tone of the user using the frequencyband of the power spectrum 430. For example, the processor 180 maydetermine a frequency band having a certain amplitude or more among thefrequency bands of the power spectrum 430 as a main register of the userand determines the determined main register as the tone of the user.

The processor 180 may determine the utterance speed of the user throughthe number of syllables uttered per unit time from the converted textdata.

The processor 180 may determine the topic uttered by the user using aBag-Of-Word Model scheme with respect to the converted text data.

The Bag-Of-Word Model scheme refers to a scheme for extracting mainlyused words based on the frequency of words in a sentence. Specifically,the Bag-Of-Word Model scheme refers to a scheme for extracting uniquewords from a sentence, expressing the frequency of the extracted wordsby a vector and determining the uttered topic as a feature.

For example, when words <running>, <physical strength>, etc. frequentlyappears in the text data, the processor 180 may classify the topicuttered by the user into an exercise.

The processor 180 may determine the topic uttered by the user from thetext data using a known text categorization scheme. The processor 180may extract keywords from the text data and determine the topic utteredby the user.

The processor 180 may determine the volume of user's voice inconsideration of the amplitude information in an entire frequency band.

For example, the processor 180 may determine the volume of user's voicebased on an average or weighted average of amplitudes in each frequencyband of the power spectrum.

The functions of the audio processor 181 and the processor 180 describedwith reference to FIGS. 3 and 4 may be performed in any one of the NLPserver 20 or the speech synthesis server 30.

For example, the NLP server 20 may extract the power spectrum using thespeech signal and determine the utterance features of the user using theextracted power spectrum.

FIG. 5 is a block diagram illustrating the configuration of a speechsynthesis server according to an embodiment of the present invention.

The speech synthesis server 30 is a device or server disposed outsidethe terminal 100 and may perform the same function as the learningprocessor 130 of the terminal 100.

That is, the speech synthesis server 30 may be configured to receive,classify, store and output information to be used for data mining, dataanalysis, intelligent decision, mechanical learning algorithms Here, themachine learning algorithms may include a deep learning algorithm.

The speech synthesis server 30 may communicate with at least oneterminal 100 and derive a result by analyzing or learning data insteadof or in aid of the terminal 100. Aiding another device may meandistribution of computing power through distribution processing.

The speech synthesis server 30 is a variety of devices for learning anartificial neural network, may generally mean a server, and may bereferred to as a learning device or a learning server.

In particular, the speech synthesis server 30 may be implemented notonly as a single server but also as a plurality of server sets, a cloudserver or a combination thereof.

That is, a plurality of speech synthesis servers 30 may configure alearning device set (or a cloud server) and at least one speechsynthesis server 30 included in the learning device set may derive aresult by analyzing or learning data through distribution processing.

The speech synthesis server 30 may transmit a model learned by machinelearning or deep learning to the terminal 100 periodically or accordingto a request.

Referring to FIG. 5, the speech synthesis server 30 may include acommunication unit 210, an input unit 220, a memory 230, a learningprocessor 240, a power supply 250 and a processor 260.

The communication unit 210 may correspond to a component including thewireless communication unit 110 and the interface 160 of FIG. 1. Thatis, data may be transmitted to and received from another device throughwired/wireless communication or an interface.

The input unit 220 may correspond to the input unit 120 of FIG. 1 andacquire data by receiving data through the communication unit 210.

The input unit 220 may acquire input data for acquiring output usingtraining data for model learning or a trained model.

The input unit 220 may acquire raw input data. In this case, theprocessor 260 may preprocess the acquired data to generate training dataor preprocessed input data capable of being input to model learning.

At this time, preprocessing of the input data performed by the inputunit 220 may mean extraction of input features from the input data.

The memory 230 may correspond to the memory 170 of FIG. 1.

The memory 230 may include a model storage unit 231 and a database 232.

The model storage unit 231 stores a model (or an artificial neuralnetwork 231 a) which is learned or being learned through the learningprocessor 240 and stores an updated model when the model is updatedthrough learning.

At this time, the model storage unit 231 may classify and store thetrained model into a plurality of versions according to a learning timepoint or learning progress, as necessary.

The artificial neural network 231 a shown in FIG. 2 is merely an exampleof the artificial neural network including a plurality of hidden layersand the artificial neural network of the present invention is notlimited thereto.

The artificial neural network 231 a may be implemented in hardware,software or a combination of hardware and software. When some or thewhole of the artificial neural network 231 a is implemented in software,one or more commands configuring the artificial neural network 231 a maybe stored in the memory 230.

The database 232 stores the input data acquired by the input unit 220,learning data (or training data) used for model learning, or a learninghistory of a model.

The input data stored in the database 232 may be not only data processedto suit model learning but also raw input data.

The learning processor 240 corresponds to the learning processor 130 ofFIG. 1.

The learning processor 240 may train or learn the artificial neuralnetwork 231 a using training data or a training set.

The learning processor 240 may immediately acquire data obtained bypreprocessing the input data acquired by the processor 260 through theinput unit 220 to learn the artificial neural network 231 a or acquirethe preprocessed input data stored in the database 232 to learn theartificial neural network 231 a.

Specifically, the learning processor 240 may determine the optimizedmodel parameters of the artificial neural network 231 a, by repeatedlylearning the artificial neural network 231 a using the above-describedvarious learning schemes.

In this specification, the artificial neural network having parametersdetermined through learning using training data may be referred to as atraining model or a trained model.

At this time, the training model may infer a result value in a state ofbeing installed in the speech synthesis server 30 of the artificialneural network and may be transmitted to and installed in another devicesuch as the terminal 100 through the communication unit 210.

In addition, when the training model is updated, the updated trainingmodel may be transmitted to and installed in another device such as theterminal 100 through the communication unit 210.

The power supply 250 corresponds to the power supply 190 of FIG. 1.

A repeated description of components corresponding to each other will beomitted.

FIGS. 6 and 7 are views illustrating a class imbalance problem when areading break is predicted through a conventional synthesized speech.

FIG. 6 is a view showing a result of performing reading with breakthrough a synthesized speech at a synthesized speech engine with respectto one sentence 600.

The synthesized speech engine may convert text into speech and outputthe speech.

The synthesized speech engine may be provided in the terminal 100 or thespeech synthesis server 30.

A space bar 601 indicates that reading break is 1, </> 603 indicatesthat the reading break is 2 and <//> 605 indicates that the readingbreak is 3.

The reading break may indicate a time interval when text is read. Thatis, as the reading break increases, the time interval when text is readmay increase. In contrast, as the reading break decreases, the timeinterval when text is read may decrease.

FIG. 7 shows a class table 700 indicating a result of analyzing thereading break with respect to the sentence 600 of FIG. 6.

The class table 700 may include a word phrase (WP) class, an accentualphrase (AP) class and an intonation phrase (IP) class.

The word phrase class indicates that reading break is 1 and may indicatea class that words are read without break.

The accentual phrase class indicates that reading break is 2 and mayindicate that break between words is small.

The intonation phrase class indicates that reading break is 3 and mayindicate that break between words is large.

In the sentence 600 of FIG. 6, the count of word phrase classes is 7,the count of accentual phrase classes is 19 and the count of intonationphase classes is 4.

A class with a smallest count is called a minor class and a class with alargest count is called a major class.

In FIG. 7, the intonation phrase class may be the minor class and theaccentual phrase class may be the major class.

When class imbalance in which the count of intonation phrase classes isless than the count of the other classes occurs, in a machine learningprocess of reading with break through a synthesized speech, theintonation phrase class may be determined as being less important andreading break performance of the synthesized speech model maydeteriorate.

Specifically, for reading break learning of the synthesized speechmodel, a training set including one sentence (training data) andlabeling data for labeling words configuring the sentence with readingbreaks is required.

When data with class imbalance is used as labeling data, performance ofthe synthesized speech model may deteriorate.

When performance of the synthesized speech model deteriorates, readingwith break may become unnatural when the synthesized speech is outputand thus users may feel uncomfortable when listening to the synthesizedspeech.

In order to solve such a problem, in the present invention, the countsof classes are adjusted in a balanced way, thereby improving readingbreak prediction performance

FIG. 8 is a flowchart illustrating a method of operating a speechsynthesis server according to an embodiment of the present invention.

The processor 260 of the speech synthesis server 30 acquires priorinformation of each of a plurality of words corresponding to the minorclass (S801).

Hereinafter, assume that the minor class is the intonation phrase classof FIG. 7.

A word belonging to (or being classified as) the intonation phrase classmeans that a word located before <//> indicating reading break of 3,such as <government's> shown in FIG. 6, belongs to the intonation phraseclass.

In one embodiment, the prior information may include one or more of anintonation phrase (hereinafter referred to as IP) ratio of a word, an IPfrequency number, a non-IP ratio, a non-IP frequency number, or a ratioof the non-IP frequency number to the IP frequency number.

The IP ratio may indicate a ratio in which a word is classified as theIP class, in the database 232. Specifically, in 10000 sentences in thedatabase 232, when the number of times of classifying a first word intoan IP class is 100, the IP ratio of the first word may be1%(100/10000×100).

In the 10000 sentences, when the number of times of classifying a secondword into the IP class is 200, the IP ratio of the second word may be2%.

Of course, only some of the 10000 sentences may include the first wordor the second word.

The IP frequency number may indicate the number of times of classifyinga word into the IP class in the database 232. In the above example, theIP frequency number of the first word may be 100 and the IP frequencynumber of the second word may be 200.

The non-IP ratio may indicate a ratio of a word classified as a classother than the IP class in the database 232.

For example, in 10000 sentences of the database 232, when the number oftimes of classifying the first word into a class other than the IP classis 500, the non-IP ratio of the first word may be 5%(500/10000×100).

The non-IP frequency number may indicate the number of times in whichthe word is not classified as the IP class in the database 232.

For example, in 10000 sentences of the database, when the number oftimes in which the first word is not classified as the IP class is 300,the non-IP ratio of the first word may be 3%(300/10000×100).

The processor 260 of the speech synthesis server 30 performs dataaugmentation with respect to each data based on the acquired priorinformation (S803).

In one embodiment, data augmentation may be a process of increasing afrequency number in which a word belongs to a specific class in order toincrease a probability that the word belongs to the specific class.

Increasing the frequency number in which the word belongs to thespecific class may indicate that the number of sentences including theword belonging to the specific class increases.

This may be interpreted as increasing a training set for learning of thesynthesized speech model.

This will be described in detail below.

The processor 260 of the speech synthesis server 30 stores a result ofperforming data augmentation in the database 232 (S805).

The processor 260 of the speech synthesis server 30 or the learningprocessor 240 performs machine learning for reading with break using thestored result of performing data augmentation (S807).

Machine learning for reading with break may be a process of determiningwith which break the words configuring a sentence is read when thesentence is input.

That is, machine learning for reading with break may be learning forclassifying one sentence into a word phrase class, an accentual phraseclass and an intonation phrase class.

A synthesized speech model may be generated according to machinelearning for reading with break.

The synthesized speech model may refer to a model for receiving onesentence as input data and outputting synthesized speech data in whichwords configuring one sentence are classified into three optimizedreading break classes.

The processor 260 of the speech synthesis server 30 may transmit thegenerated synthesized speech model to the terminal 100 through thecommunication unit 210.

FIG. 9 is a flowchart illustrating a process of performing dataaugmentation of a word based on prior information according to anembodiment of the present invention.

In particular, FIG. 9 is a view illustrating steps S803 and S805 shownin FIG. 8 in detail.

The processor 260 of the speech synthesis server 30 determines theoversampling rate of each word based on the prior information of theword (S901)

In one embodiment, the processor 260 may determine the oversampling rateof the word based on the ratio of the non-IP frequency number to the IPfrequency number of the word classified as the minor class.

The oversampling rate may indicate a rate at which the word belongs tothe IP class in the database 232.

The processor 260 may increase the oversampling rate as the ratio of thenon-IP frequency number to the IP frequency number of the wordincreases.

The processor 260 may decrease the oversampling rate as the ratio of thenon-IP frequency number to the IP frequency number of the wordincreases.

This will be described with reference to FIG. 10.

FIG. 10 is a view showing an IP frequency number and a non-IP frequencynumber of each word stored in a database according to an embodiment ofthe present invention.

FIG. 10 shows a result obtained by measuring reading break afteruttering a specific word when a voice actor utters a large number ofsentences, in order to generate a synthesized speech.

For example, assume that the frequency number in which a word <but> isclassified as the IP class in the database 232 is 60 and the frequencynumber in which the word <but> is classified as the non-IP class insteadof the IP class is 10.

Since the ratio of the non-IP frequency number to the IP frequencynumber is 1:6, the processor 260 may determine that the oversamplingrate of the word <but> is 60% (6/1×0.1).

For example, the processor 260 may increase the existing frequencynumber, in which the word <but> is classified as the IP class, to 96which is greater than 60 by 60%.

In another example, assume that the frequency number in which a word<can> is classified as the IP class in the database 232 is 30 and thefrequency number in which the word <can> is classified as the non-IPclass instead of the IP class is 120.

Since the ratio of the non-IP frequency number to the IP frequencynumber is 4:1, the processor 260 may determine that the oversamplingrate of the word <can> is 2.5% (1/4×0.1).

For example, the processor 260 may increase the existing frequencynumber, in which the word <can> is classified as the IP class, to 3.075which is greater than 30 by 2.5%.

In another example, the processor 260 may increase the oversampling rateonly when the IP frequency number of the word is greater than the non-IPfrequency number of the word.

In contrast, the processor 260 may not perform oversampling of the wordwhen the IP frequency number of the word is less than the non-IPfrequency number of the word. That is, the processor 260 may fix theoversampling rate when the IP frequency number of the word is less thanthe non-IP frequency number of the word.

FIG. 11 is a view illustrating an oversampling rate determined accordingto a ratio of a non-IP frequency number to an IP frequency number.

FIG. 11 shows the oversampling rate determined according to the ratio ofthe non-IP frequency number to the IP frequency number of the word ofFIG. 10 in the 10000 sentences stored in the database 232.

That is, FIG. 11 shows the non-IP frequency number in which each word isnot classified as the IP class, the IP frequency number in which eachword is classified as the IP class, the relative ratio of non-IPfrequency number to the IP frequency number, and the oversampling ratedetermined according to the relative ratio.

As can be seen from FIG. 11, as the relative ratio increases, theoversampling rate increases. As the relative ratio decreases, theoversampling rate decreases.

When the oversampling rate increases, a probability that the word isclassified as the IP class may increase.

When the probability that the word is classified as the IP classincreases, the class imbalance can be solved and the reading breakperformance of the synthesized speech model may increase.

FIG. 9 will be described again.

The processor 260 of the speech synthesis server 30 determines thenumber of times of oversampling of the word using the determinedoversampling rate (S903).

In one embodiment, the number of times of oversampling of the word mayindicate the IP frequency number to be increased based on the determinedoversampling rate of the word.

The IP frequency number to be increased may indicate the number ofsentences including the word classified as the IP class.

That is, increasing the number of times of oversampling of the word mayindicate that the number of sentences including the word classified asthe IP class increases.

In one embodiment, the processor 260 may determine the number of timesof oversampling of the word based on the oversampling rate determined instep S901.

In another embodiment, the processor 260 may determine the number oftimes of oversampling the word, based on the oversampling rate, thenumber of words classified as the major class in the database 232, thenumber of words classified as the minor class, the number of times oflabeling the word with the minor class, a probability that the wordbelongs to the minor class, and the number of times in which the wordappears in the database 232.

Specifically, the processor 260 may determine the number of times ofoversampling as shown in Equation 1 below.

$\begin{matrix}{{word}_{i:{over}} = {{SamplingRate}*\frac{{Class}_{Major}}{{Class}_{minor}}*{{{word}_{i} = {minor}}}*{P( {word}_{i:{minor}} )}}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

where, word_(i) may indicate a specific word present in the database232,

word_(i:over) may indicate the number of times of oversampling ofword_(i),

Sampling Rate may be a constant determined in step S901 and may have avalue of 10% to 100%, but this is merely an example,

|Class_(Major)| may indicate the number of words in the major class,

|Class_(Minor)| may indicate the number of words in the minor class, and

P(word_(i=minor)) may indicate a probability that a specific wordbelongs to the minor class.

P(word_(i=minor)) may be expressed by Equation 2 below.

$\begin{matrix}\frac{{{word}_{i} = {minor}}}{{word}_{i}} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack\end{matrix}$

where, |Word_(i)=minor| may indicate the number of times in which word,is labeled with the minor class in the database 232.

Labeling the word with the minor class may mean that words<government's>, <year>, <rain> and <Monday> which are used as criteriaused to determine the count of the IP class which is the minor class areclassed into the IP class, in FIGS. 6 and 7.

|word_(i)| may indicate the number of times in which word, appears inthe database 232.

That is, |word_(i)| may indicate the number of times in which word,appears in a plurality of sentences of the database 232.

The processor 260 of the speech synthesis server 30 stores thedetermined number of times of oversampling in the database 232 (S905).

The processor 260 may generate sentences including the words, the numberof which correspond to the determined number of times of oversamplingthe word.

The processor 260 may label the word with the IP class and generatesentences including the word labeled with reading break of 3 such thatthe number of sentences corresponds to the number of times ofoversampling.

The processor 260 may learn the synthesized speech model using thesentences including the word and the labeling data of labeling the wordwith reading break.

FIG. 12 is a ladder diagram illustrating a method of operating a systemaccording to an embodiment of the present invention.

Referring to FIG. 12, the speech synthesis server 30 acquires sentencesincluding the word classified as the IP class by the number of times ofoversampling of the word (S1201).

The speech synthesis server 30 may generate arbitrary sentencesincluding the word.

The arbitrary sentences may be training data for learning of thesynthesized speech model.

The speech synthesis server 30 learns the synthesized speech model usingthe acquired sentences (S1203).

The word classified as the IP class may be labeled with reading break of3.

The speech synthesis server 30 may learn the synthesized speech modelusing the arbitrary sentences (training data) and the labeling data oflabeling the word in the arbitrary sentences with the reading break.

In one embodiment, the processor 260 of the speech synthesis server 30may learn the synthesized speech model using a recurrent neural network(RNN).

The recurrent neural network is a kind of artificial neural network inwhich a hidden layer is connected to a directional edge to form arecurrent structure.

A process of learning the synthesized speech model using the recurrentneural network will be described with reference to FIG. 13.

FIG. 13 is a view illustrating a basic structure of a recurrent neuralnetwork.

Xt denotes input data, Ht denotes current hidden data, H(t-1) denotesprevious hidden data, and Yt denotes output data.

The input data, the hidden data and the output data may be expressed byfeature vectors.

Parameters learned by the RNN include a first parameter W1 forconverting the previous hidden data into the current hidden data, asecond parameter W2 for converting the input data into the hidden dataand a third parameter W3 for converting the current hidden data into theoutput data.

The first, second and third parameters W1, W2 and W3 may be expressed bya matrix.

According to the present invention, the input data may be a featurevector indicating a word, and the output data may be a feature vectorindicating a first probability that an input word belongs to a WP class,a second probability that the input word belongs to an AP class and athird probability that the input word belongs to an IP class.

The previous hidden data may be hidden data of a previously input word,and the current hidden data may be data generated using the hidden dataof the previously input word and a feature vector of a currently inputword.

FIG. 14 is a view illustrating a process of classifying wordsconfiguring a sentence into classes using a synthesized speech modelaccording to an embodiment of the present invention.

Referring to FIG. 14, a plurality of words 1310 configuring one sentenceis sequentially input to the synthesized speech model 1330.

The terminal 100 or the speech synthesis server 30 may output a firstprobability that each of the sequentially input words 1310 is classifiedas the WP class, a second probability that each of the sequentiallyinput words 1310 is classified as the AP class and a third probabilitythat each of the sequentially input words 1310 is classified as the IPclass, using the synthesized speech model 1330.

The terminal 100 or the speech synthesis server 30 may classify aprobability having the largest value among the first to thirdprobabilities into the class of the input word.

FIG. 12 will be described again.

The speech synthesis server 30 transmits the learned synthesized speechmodel to the terminal 100 (S1205).

The terminal 100 outputs the synthesized speech according to the requestof the user through the audio output unit 152 using the synthesizedspeech model received from the speech synthesis server 30 (S1207).

The request of the user may be the speech command of the user, such as<Read news article>.

The terminal 100 may receive the speech command of the user and graspthe intention of the received speech command

The terminal 100 may output, through the audio output unit 152, thesynthesized speech of the text corresponding to the news article suitingthe grasped intention using the synthesized speech model.

FIG. 15 is a flowchart illustrating a method of operating a speechsynthesis server using artificial intelligence according to anotherembodiment of the present invention.

Referring to FIG. 15, the processor 260 of the speech synthesis server30 acquires prior information of each of a plurality of wordscorresponding to a minor class (S1501).

Hereinafter, assume that the minor class is the intonation phrase classof FIG. 7.

A word belonging to (or being classified as) the intonation phrase classmeans that a word located before <//> indicating reading break of 3,such as <government's> shown in FIG. 6, belongs to the intonation phraseclass.

In one embodiment, the prior information may include one or more of anintonation phrase (hereinafter referred to as IP) ratio of a word, an IPfrequency number, a non-IP ratio in which the word does not belong tothe intonation phrase class (hereinafter referred to as a non-IP ratio),a non-IP frequency number, or a ratio of the non-IP frequency number tothe IP frequency number.

The IP ratio may indicate a ratio in which a word is classified as theIP class, in the database 232. Specifically, in 10000 sentences in thedatabase 232, when the number of times of classifying a first word intoan IP class is 100, the IP ratio of the first word may be1%(100/10000×100).

FIG. 16 is a diagram illustrating prior information of each word storedin a database according to an embodiment of the present invention.

FIG. 16 shows an IP table 1600 showing an IP ratio in which each word isclassified as the IP class and a non-IP ratio in which each word is notclassified as the IP class.

The IP table 1600 shows the IP ratio which is the ratio in which eachword is classified as the IP class in the sentences stored in thedatabase 232 and the non-IP ratio obtained by subtracting the IP ratiofrom 1, with respect to each of the plurality of words.

The non-IP ratio may be a sum of the ratio in which the word isclassified as the WP class and the ratio in which the word is classifiedas the AP class.

For example, the IP ratio of the word “Because” is 0.84 and the non-IPratio thereof is 0.16 (1−0.84).

In addition, the IP ratio of the word “This” is 0.15 and the non-IPratio thereof is 0.85.

FIG. 15 will be described again.

The processor 260 of the speech synthesis server 30 acquires a firstclass classification probability set indicating the per-classclassification probability of each word used as labeling data of thesynthesized speech model.

The synthesized speech model may be an artificial neural network basedmodel learned by a machine learning algorithm or a deep learningalgorithm.

For example, the synthesized speech model may be a recurrent neuralnetwork based model shown in FIG. 13.

The first class classification probability set may include a probabilitythat the word is classified as the WP class, a probability that the wordis classified as the AP class and a probability that the word isclassified as the IP class, within one sentence.

Specifically, a first probability that the word is classified as the WPclass may indicate a probability of reading a word with break of 1within one sentence.

Similarly, a second probability that the word is classified as the APclass may indicate a probability of reading a word with break of 2within one sentence, and a third probability that the word is classifiedas the IP class may indicate a probability of reading a word with breakof 3 within one sentence.

The processor 260 may infer a probability that each word is classifiedas the WP class, a probability that each word is classified as the APclass and a probability that each word is classified as the IP class,using the synthesized speech model.

The synthesized speech model may be a model composed of an artificialneural network learned to infer a first class classification probabilityset indicating the output feature point using a sentence including aplurality of words as input data.

For example, the synthesized speech model may be learned throughsupervised learning. Specifically, learning data used for thesynthesized speech model may be labeled with the probability that theword is classified as the WP class, the probability that the word isclassified as the AP class and the probability that the word isclassified as the IP class.

The synthesized speech model may be learned using the labeled learningdata.

The synthesized speech model may be learned with the goal of accuratelyinferring the probability that the word included in text data isclassified as the labeled WP class, the probability that the wordincluded in text data is classified as the AP class and the probabilitythat the word included in text data is classified as the IP class, fromtext data for learning.

The weighted cost function of the synthesized speech model may beexpressed by a squared mean of a difference between each classprobability corresponding to each learning data and each classprobability inferred from learning data.

Through learning of the synthesized speech model, model parametersincluded in the artificial neural network may be determined to minimizethe value of the weighted cost function.

FIG. 17 is a diagram illustrating an example of a synthesized speechmodel according to an embodiment of the present invention.

Referring to FIG. 17, a synthesized speech model 1700 composed of anartificial neural network is shown.

Text data which is learning data and a per-class probability which islabeling data may be input to the synthesized speech model 1700 as onetraining set.

As a result of inference, the per-class probability may be output.

The synthesized speech model 1700 may be learned to minimize the costfunction corresponding to a difference between the output per-classprobability and the labeled per-class probability.

The synthesized speech model 1700 may be learned, such that a result ofinferring each per-class classification probability is output as atarget feature vector and a cost function corresponding to a differencebetween the output per-class classification probability set and thelabeled per-class classification probability set is minimized, when aninput feature vector is extracted from the text data including words andinput to the synthesized speech model.

The output result of the synthesized speech model 1700 may be composedof an output layer having a plurality of output nodes indicating theper-class classification probability of the word.

Each of the plurality of output nodes may indicate the probability thatthe word is classified as the WP class, the probability that the word isclassified as the AP class and the probability that the word isclassified as the IP class.

Each of the plurality of output nodes may be expressed by a targetfeature vector such as (0.3, 0.3, 0.4). Each of the values of theelements configuring the target feature vector may have a value of 0 to1.

FIG. 15 will be described again.

The processor 260 of the speech synthesis server 30 acquires a secondclass classification probability set indicating a corrected per-classclassification probability of each word based on the prior informationand first class classification probability set of each word (S1505).

The processor 260 may correct the first class classification probabilityset to the second class classification probability set, based on the IPratio and the first class classification probability set of the word.

The processor 260 may adjust the class classification probability set tobe used as labeling data in the synthesized speech model 1700, based onthe IP ratio and the first class classification probability set of theword.

This is because labeling data is corrected by applying the IP ratio inwhich a specific word belongs to the IP class and a non-IP ratio inwhich the specific word belongs to the non-IP ratio in the plurality ofsentences stored in the database.

When labeling data, to which the IP ratio and the non-IP ratio areapplied, is used to learn the synthesized speech model, since thedistribution of the word classified as the IP class is applied, it ispossible to improve class classification accuracy.

Therefore, it is possible to solve a class imbalance problem.

A process of correcting the first class classification probability setin consideration of the IP ratio and the non-P ration of the word willbe described with reference to the following drawings.

FIGS. 18 to 21 are diagrams illustrating an example of correcting aclass classification probability set in consideration of an IP ratio anda non-IP ratio of a word according to an embodiment of the presentinvention.

First, FIGS. 18 and 19 will be described based on the word <Because>.

In addition, for the IP ratio of the word <Because>, refer to the IPtable 1600 of FIG. 16.

Referring to FIG. 18, the first class classification probability set1800 which is labeling data corresponding to the word <Because> isshown.

As the labeling data of <Because>, a probability that the word isclassified as the WP class is 0.3, a probability that the word isclassified as the AP class is 0.6, and a probability that the word isclassified as the IP class is 0.1.

In FIG. 18, each of the probability that the word is classified as theWP class, the probability that the word is classified as the AP classand the probability that the word is classified as the IP class may be amathematical probability.

The processor 260 may acquire the second class classificationprobability set 1900 shown in FIG. 19, based on the IP ratio, non-IPratio and first class classification probability set 1800 of <Because>.

The corrected WP class classification probability may be expressed asshown in Equation 3 below.

Corrected WP class classification probability=(WP class classificationprobability before correction)*(Non-IP ratio)*(probability that the wordis classified as the WP class/probability that the word is notclassified as the IP class)   [Equation 3]

Accordingly, a value of 0.3*0.16*(0.3/0.9)=0.016 may be obtained as thecorrected WP class classification probability by Equation 3.

The corrected AP class classification probability may be expressed byEquation 4 below.

Corrected AP class classification probability=(AP class classificationprobability before correction)*(Non-IP ratio)*(probability that the wordis classified as the AP class/probability that the word is notclassified as the IP class)   [Equation 4]

Accordingly, a value of 0.6*0.16*(0.6/0.9)=0.064 may be obtained as thecorrected AP class classification probability by Equation 4.

The corrected IP class classification probability may be expressed byEquation 5 below.

Corrected IP class classification probability=(IP class classificationprobability before correction)*(IP ratio)   [Equation 5]

Accordingly, a value of 0.1*0.84=0.084 may be obtained as the correctedIP class classification probability by Equation 5.

Meanwhile, the processor 260 may change each of the corrected classclassification probabilities to a normalized value based on 1.

The probability that the word <Because> is classified as the correctedWP class is 0.97, the probability that the word <Because> is classifiedas the corrected AP class is 0.390, and the probability that the word<Because> is classified as the corrected IP class is 0.513.

That is, the first class classification probability set (0.3, 0.6, 0.1)may be changed to the second class classification probability set(0.097, 0.390, 0.513).

That is, the WP class classification probability decreased from 0.3 to0.097, the AP class classification probability decreased from 0.6 to0.390, and the IP class classification probability decreased from 0.1 to0.513.

The processor 260 may increase the probability that the word isclassified as the IP class as the IP ratio of the word increases anddecreases the probability that the word is classified as the IP class asthe IP ratio decreases.

The probability that the word is classified as the IP class may increaseby correcting the labeling data in consideration of the IP ratio of theword stored in the database 232.

Therefore, when the synthesized speech is generated, a possibility thatthe word belongs to the IP class increases, thereby solving classimbalance.

Next, FIGS. 20 and 21 will be described.

FIGS. 20 and 21 will be described based on the word <This>.

In addition, for the IP ratio of the word <This>, refer to the IP table1600 of FIG. 16.

Referring to FIG. 20, the first class classification probability set2000 which is labeling data corresponding to the word <This> is shown.

As the labeling data of <This>, a probability that the word isclassified as the WP class is 0.3, a probability that the word isclassified as the AP class is 0.3, and a probability that the word isclassified as the IP class is 0.4.

The processor 260 may acquire the second class classificationprobability set 2100 shown in FIG. 21, based on the IP ratio, non-IPratio and first class classification probability set 2000 of <This>.

The corrected WP class classification probability may be expressed asshown in

Equation 3 above.

A value of 0.3*0.85*(0.3/0.6)=0.127 may be obtained as the corrected WPclass classification probability by Equation 3.

The corrected AP class classification probability may be expressed byEquation 4 above.

A value of 0.3*0.85*(0.3/0.6)=0.127 may be obtained as the corrected APclass classification probability by Equation 4.

The corrected IP class classification probability may be expressed byEquation 5 above.

A value of 0.4*0.15=0.06 may be obtained as the corrected IP classclassification probability by Equation 5.

Meanwhile, the processor 260 may change each of the corrected classclassification probabilities to a normalized value based on 1.

The probability that the word <This> is classified as the corrected WPclass is 0.4, the probability that the word <This> is classified as thecorrected AP class is 0.4, and the probability that the word <This> isclassified as the corrected IP class is 0.2.

That is, the first class classification probability set (0.3, 0.3, 0.4)may be changed to the second class classification probability set (0.4,0.4, 0.2).

That is, the WP class classification probability increased from 0.3 to0.4, the AP class classification probability increased from 0.3 to 0.4,and the IP class classification probability decreased from 0.4 to 0.2.

The probability that the word is classified as the IP class may decreaseby correcting the labeling data in consideration of the IP ratio of theword stored in the database 232.

Therefore, when the synthesized speech is generated, a possibility thatthe word belongs to the IP class decreases, thereby solving classimbalance.

That is, according to the embodiment of the present invention, it ispossible to improve reading break prediction performance of thesynthesized speech model.

FIG. 15 will be described again.

The processor 260 of the speech synthesis server 30 or the learningprocessor 240 learns the synthesized speech model using the acquiredsecond class classification probability set (S1507).

The processor 260 may learn the synthesized speech model using theacquired second class classification probability set as new labelingdata.

A process of learning the synthesized speech model using the secondclass classification probability set will be described with reference toFIG. 22.

FIG. 22 is a diagram illustrating a process of learning a synthesizedspeech model using a newly acquired second class classificationprobability set based on an IP ratio according to an embodiment of thepresent invention.

Referring to FIG. 22, a training set including text data including wordsand class classification probability set of each word may be input tothe synthesized speech model 1700.

The synthesized speech model 1700 may output a first classclassification probability set 2210 including a probability that eachword is classified as the WP class, a probability that each word isclassified as the AP class and a probability that each word isclassified as the IP class, with respect to the training set.

The processor 260 may acquire a second class classification probabilityset 2230 based on the output first class classification probability set2210 and the IP ratio and non-IP ratio of each word.

That is, the processor 260 may perform probability correction operationto change the first class classification probability set 2210 to thesecond class classification probability set 2230, as shown in FIGS. 18to 21.

The processor 260 may use the newly acquired second class classificationprobability set 2230 as new labeling data of the synthesized speechmodel 1700.

Meanwhile, the synthesized speech models described with reference toFIGS. 15 to 22 may be transmitted to the terminal.

The terminal may obtain the per-class classification probability of eachword included in text data corresponding to a sentence using thesynthesized speech mode.

FIG. 23 is a ladder diagram illustrating a method of operating anothersystem of the present invention.

In particular, FIG. 23 relates to a method of outputting a synthesizedspeech in consideration of a reading-with-break style of a user.

The processor 260 of the speech synthesizer 30 acquires an IP ratiotable of each of a plurality of voice actors based on the plurality ofvoice actors stored in the database 232 (S2301).

The database 232 stores speech data uttered by each of the plurality ofvoice actors.

The processor 260 may acquire the IP ratio table based on the speechdata uttered by each voice actor. The IP ratio table may include an IPratio in which the plurality of words is classified as an IP class and anon-IP ratio which the plurality of words is not classified as an IPclass.

This will be described with reference to FIG. 24.

FIG. 24 is a view illustrating a plurality of IP tables respectivelycorresponding to a plurality of voice actors according to an embodimentof the present invention.

The processor 260 may acquire the IP ratio of each word based on thespeech data corresponding to the speech uttered by each voice actor.

Each of the plurality of voice actors 2401 to 2403 may utter words withdifferent breaks according to the unique utterance style thereof, evenif the words are the same.

Referring to FIG. 24, a first IP ratio table 2410 obtained based on thespeech uttered by the first voice actor 2401, a second IP ratio table2430 obtained based on the speech uttered by a second voice actor 2403and a third IP table 2450 obtained based on the speech uttered by athird voice actor 2405 are shown.

The first IP ratio table 2410 includes an IP ratio in which the firstvoice actor 2401 reads each of a plurality of words with breakcorresponding to the IP class and a non-IP ratio in which the firstvoice actor 2401 reads each of a plurality of words with breakcorresponding to the non-IP class.

The second IP ratio table 2430 includes an IP ratio in which the secondvoice actor 2403 reads each of a plurality of words with breakcorresponding to the IP class and a non-IP ratio in which the firstvoice actor 2403 reads each of a plurality of words with breakcorresponding to the non-IP class.

The second IP ratio table 2450 includes an IP ratio in which the secondvoice actor 2405 reads each of a plurality of words with breakcorresponding to the IP class and a non-IP ratio in which the firstvoice actor 2405 reads each of a plurality of words with breakcorresponding to the non-IP class.

In FIG. 24, the IP ratio tables of three voice actors are described butthis is merely an example and IP ratio tables of more voice actors maybe obtained.

FIG. 23 will be described.

The processor 260 of the speech synthesizer 30 acquires a normal IPratio table indicating a normal IP ratio of each word using theplurality of acquired IP ratio tables (S2303).

The processor 260 may calculate an average of the IP ratios of each wordincluded in each of the plurality of IP ratio tables.

For example, when the IP ratios of three voice actors for each word area1, a2 and a3, the normal IP ratio may be (a1+a2+a3)/3.

This will be described with reference to FIG. 25.

FIG. 25 is a view illustrating a normal IP ratio table according to anembodiment of the present invention.

FIG. 24 is used to describe FIG. 25.

Referring to FIG. 25, the normal IP ratio table 2500 is shown.

The IP ratio of each word included in the normal IP ratio table 2500 maybe obtained by the average of the IP ratios of each word included ineach of the IP ratio tables shown in FIG. 24.

For example, the normal IP ratio of a word <Because> will be described.

The IP ratio of <Because> is 0.84 in the first IP ratio table 2410, is0.80 in the second IP ratio table 2430, and is 0.70 in the third IPratio table 2450.

The normal IP ratio of <Because> is 0.780, by calculating(0.84+0.80+0.70)/3.

The normal non-IP ratio of <Because> may be obtained by subtracting thenormal IP ratio from 1.

In this manner, the normal IP ratio of each of the plurality of wordsmay be calculated and the normal IP ratio table 2500 which is acombination of the normal IP ratios may be obtained.

As described below, the normal IP ratio table 2500 may be used to trainthe normal synthesized speech model.

FIG. 23 will be described again.

The processor 260 of the speech synthesizer 30 generates a normalsynthesized speech model based on the acquired normal IP ratio table(S2305).

The normal synthesized speech model may be a model for determining aprobability that a word is classified as an IP class, a probability thata word is classified as a WP class and a probability that a word isclassified as an AP class, using the normal IP ratio of each wordincluded in the normal IP ratio table.

After the normal synthesized speech model is trained, the reading breakof the word may be determined according to the class having the highestprobability among the determined probabilities when the synthesizedspeech is generated.

The normal synthesized speech model may be an artificial neural networkbased model learned by a deep learning algorithm or a machine learningalgorithm.

The normal synthesized speech model may be learned through supervisedlearning.

Learning data used for the normal synthesized speech model may includetext data corresponding to a sentence including a plurality of words, anormal IP ratio of each of the plurality of words, and an IP classclassification probability labeled with each word.

Detailed description of the normal synthesized speech model may bereplaced with the embodiment of FIG. 17.

The processor 260 of the speech synthesizer 30 transmits the generatednormal synthesized speech model to the terminal 100 through thecommunication unit 210 (S2307).

The terminal 100 stores the normal synthesized speech model receivedfrom the speech synthesizer 30 in the memory 170 and collect utteranceinformation of the user (S2309).

The terminal 100 may output a speech based on the normal synthesizedspeech model.

The terminal 100 may receive the speech data uttered by the user andacquire an intention of the received speech data.

The terminal 100 may acquire text corresponding to the acquiredintention and output a synthesized speech corresponding to the acquiredtext using the normal synthesized speech model. The terminal 100 mayoutput the synthesized speech, to which the reading break of each wordincluded in the synthesized speech is applied.

The terminal 100 may collect utterance information based on the speechdata uttered by the user.

The utterance information may include the number of times of readingwords configuring a sentence uttered by the user in the IP class, thepart of speech of the word, and the position of the word in thesentence.

The processor 260 of the speech synthesizer 30 receives the utteranceinformation of the user collected by the terminal 100 through thecommunication unit 210 (S2311).

The processor 260 may use the received utterance information to acquirea personalized IP ratio table.

The personalized IP ratio table may be data used to train thepersonalized synthesized speech model. The personalized IP ratio tablemay include IP ratios of each word applied to a specific person.

The processor 260 of the speech synthesizer 30 acquires the utterance IPratio of each of a plurality of uttered words based on the receivedutterance information of the user (S2313).

The utterance IP ratio may be an IP ratio correspond to each of theplurality of words uttered by the user.

The utterance IP ratio may be a ratio in which the words uttered by theuser are read with break corresponding to the IP class.

The processor 260 may change the normal IP ratio of each word used inthe normal synthesized speech model to a newly acquired utterance IPratio.

This will be described with reference to FIG. 26.

FIG. 26 is a view illustrating a table including personalized IP ratiosand normal IP ratios of acquired words based on utterance information ofa user.

Referring to FIG. 26, a table 2600 includes a normal IP ratio 2610 and apersonalized IP ratio 2630 of each of a plurality of words.

For example, the normal IP ratio of a word <Because> obtained based onutterance of the plurality of voice actors may be 0.78 and thepersonalized IP ratio of the word <Because> obtained based on utteranceof a specific person may be 0.75.

For example, the personalized IP ratio may be obtained through thenumber of times that the user reads the word <Because> included in 100sentences with break corresponding to the IP class.

In addition, the normal IP ratio of a word <For> obtained based onutterance of the plurality of voice actors may be 0.697 and thepersonalized IP ratio of the word <For> obtained based on utterance of aspecific person may be 0.65.

That is, the IP ratio may be changed to generate the personalizedsynthesized speech model.

The personalized synthesized speech model may be a personalized modelfor outputting a synthesized speech, to which the reading-with-breakstyle of the user is applied.

The personalized synthesized speech model may be a model for outputtinga synthesized speech optimized for the user who receives the speechrecognition service through the terminal 100.

Meanwhile, the collected utterance information of the user requirespersonalized IP ratios of words unuttered by the user.

That is, referring to FIG. 26, words <We>, <And> and <This> areunuttered by the user and thus the personalized IP ratios thereof maynot be directly calculated.

To this end, the processor 260 may estimate the normal IP ratios of theunuttered words.

FIG. 24 will be described again.

The processor 260 of the speech synthesizer 30 estimates thenon-utterance IP ratios respectively corresponding to the unutteredwords based on the utterance information and the acquired utterance IPratios (S2315).

The utterance information may include the part of speech of the worduttered by the user, the length of the uttered sentence and the positionof the uttered word in the sentence.

The processor 260 may estimate the non-utterance IP ratios of theunuttered words based on the utterance information and the personalizedIP ratios of the uttered words.

The processor 260 may determine the IP ratio of the unuttered word basedon the IP ratio model.

The IP ratio model may be a model for determining a probability that theunuttered word is classified as an IP class, using the unuttered word,the property of the unuttered word, an IP ratio of the uttered wordhaving a property similar to that of the unuttered word, and labelingdata (a probability of being classified as the IP class).

The uttered word having the property similar to that of the unutteredword may be a word similar to the unuttered word.

The processor 260 may determine the probability that the word isclassified as the IP class as the IP ratio of the unuttered word.

This will be described with reference to FIG. 27.

FIG. 27 is a view illustrating an IP ratio model according to anembodiment of the present invention.

The IP ratio model 2700 may be a model for estimating the IP ratio of aword unuttered by the user.

The IP ratio model may be an artificial neural network based modellearned by a deep learning algorithm or a machine learning algorithm.

Learning data used to train the IP ratio model may include an unutteredword, a property of the unuttered word, and labeling data (a probabilityof being classified as the IP class).

The property of the unuttered word may include one or more of the partof speech of the unuttered word or the position of the unuttered word inthe sentence.

The IP ratio model 2700 may be a model for accurately inferring theprobability that the unuttered word is classified as the IP class,using, as input data, an unuttered word, a property of the unutteredword, and the probability that the word is classified as the IP class.

The labeling data may be a personalized IP ratio of an uttered wordhaving the same part of speech as an unuttered word and having aposition in the sentence similar to that of the unuttered word.

The processor 260 may acquire the personalized IP ratio of the wordunuttered by the user using the IP ratio model 2700.

FIG. 28 is a view illustrating a result of estimating personalized IPratios of words unuttered by a user according to an embodiment of thepresent invention.

Referring to the table 2800 of FIG. 28, personalized IP ratios 2810(non-utterance IP ratios) of the words <We>, <And> and <This> unutteredby the user, which are estimated using the IP ratio model 2700, may beincluded.

The personalized IP ratios respectively corresponding to the wordsunuttered by the user may be used to train the personalized synthesizedspeech model.

FIG. 23 will be described again.

The processor 260 of the speech synthesizer 30 generates a personalizedsynthesized speech model based on the utterance IP ratios and theestimated non-utterance IP ratios (S2317).

The processor 260 may generate the personalized synthesized speech modelbased on the IP ratios of the uttered words and the non-utterance IPratios.

The personalized synthesized speech model may be a model for outputtingthe synthesized speech, to which the reading-with-break style of theuser is applied.

The method of training the personalized synthesized speech model may beequal to the method of training the synthesized speech model shown inFIG. 17. However, as the IP ratios used as the learning data, thepersonalized IP ratios shown in FIG. 28 may be used.

The personalized synthesized speech model may be an artificial neuralnetwork based model learned by a deep learning algorithm or a machinelearning algorithm.

The processor 260 may apply the oversampling scheme described withreference to FIGS. 8 and 9 to the personalized synthesized speech model,in order to increase reading break prediction performance.

In another example, the processor 260 may apply the embodiment of FIG.15 to the personalized synthesized speech model in order to increasereading break prediction performance.

The processor 260 of the speech synthesizer 30 transmits thepersonalized synthesized speech model to the terminal 100 through thecommunication unit 210 (S2319).

The terminal 100 may store the personalized synthesized speech model inthe memory 170.

The terminal 100 may output the synthesized speech suiting thereading-with-break style of the user when the speech recognition serviceis provided to the user.

Therefore, the user can listen to the speech suiting the utterance stylethereof, thereby greatly improving satisfaction with the speechrecognition service.

Meanwhile, when utterance information of words unuttered by the user arecollected, the processor 260 may update the personalized synthesizedspeech model.

This will be described with reference to FIG. 29.

FIG. 29 is a flowchart illustrating a process of updating a personalizedsynthesized speech model at a speech synthesizer according to anembodiment of the present invention.

Referring to FIG. 29, the processor 260 of the speech synthesizer 30collects the utterance information of the unuttered word (S2901).

The processor 260 may receive the utterance information of the unutteredword from the terminal 100.

The utterance information of the unuttered word may include the numberof times of reading a word in the IP class, the part of speech of theword, and the position of the word in the sentence.

The processor 260 of the speech synthesizer 30 acquires the IP ratio ofthe unuttered word based on the collected utterance information of theunuttered word (S2903).

The processor 260 may acquire the IP ratio based on the number of timesof reading the unuttered word in the IP class.

The processor 260 of the speech synthesizer 30 determines whether adifference between the acquired IP ratio and the IP ratio estimated instep S2315 is equal to or greater than a predetermined ratio (S2905).

The predetermined ratio may be 0.05 but this is merely an example.

The processor 260 of the speech synthesizer 30 retrains the personalizedsynthesized speech model when the difference between the acquired IPratio and the estimated IP ratio is equal to or greater than thepredetermined ratio, in order to accurately generate the personalizedsynthesized speech model (S2907).

When the difference between the acquired IP ratio and the estimated IPratio is large, the processor 260 may retrain the personalizedsynthesized speech model in order to accurately generate thepersonalized synthesized speech model.

That is, the processor 260 may train the personalized synthesized speechmodel by changing the estimated IP ratio of the unuttered word to the IPratio of the newly uttered word.

The processor 260 of the speech synthesizer 30 acquires the personalizedsynthesized speech model updated by retraining and transmits the updatedpersonalized synthesized speech model to the terminal 100 (S2909).

The terminal 100 may store the updated personalized synthesized speechmodel in the memory 170 and provide the speech service through theupdated personalized synthesized speech model.

Therefore, it is possible to provide the synthesized speech, to whichthe reading-with-break style of the user is applied, thereby greatlyimproving user's satisfaction with the speech recognition service.

The present invention mentioned in the foregoing description can also beembodied as computer readable codes on a computer-readable recordingmedium. Examples of possible computer-readable mediums include HDD (HardDisk Drive), SSD (Solid State Disk), SDD (Silicon Disk Drive), ROM, RAM,CD-ROM, a magnetic tape, a floppy disk, an optical data storage device,etc. The computer may include the processor 180 of the terminal.

What is claimed is:
 1. A speech synthesizer using artificialintelligence, comprising: a memory; a communication unit configured toreceive utterance information of words uttered by a user from aterminal; and a processor configured to acquire a plurality of utteranceintonation phrase (IP) ratios respectively corresponding to a pluralityof words uttered by the user based on the utterance information, acquirea plurality of non-utterance IP ratios respectively corresponding to aplurality of unuttered words based on the utterance information and theplurality of utterance IP ratios, and generate a personalizedsynthesized speech model based on the plurality of utterance IP ratiosand the plurality of non-utterance IP ratios, wherein a plurality ofclasses indicating reading break of a word includes a first classcorresponding to first reading break, a second class corresponding tosecond reading break greater than the first break and a third classcorresponding to third reading break greater than the second break,wherein a minor class has a smallest count among the first to thirdclasses, and wherein each of the utterance IP ratios and thenon-utterance IP ratios is a ratio in which a word is classified as theminor class.
 2. The speech synthesizer according to claim 1, wherein theutterance information includes reading break of each uttered word, apart of speech of each uttered word, and a position of each uttered wordin a sentence.
 3. The speech synthesizer according to claim 2, whereinthe processor acquires the utterance IP ratio of each uttered word,using the number of times that the user reads each uttered word withbreak corresponding to the minor class.
 4. The speech synthesizeraccording to claim 3, wherein the memory stores an IP ratio model fordetermining an IP ratio of an unuttered word, and wherein the processor:determines a probability in which the unuttered word is classified asthe minor class, using each unuttered word, a property of each unutteredword, an IP ratio of an uttered word and labeling data (a probability ofbeing classified as the minor class), and determines a probability ofbeing classified as a determined IP class as a non-utterance IP ratio ofthe unuttered word.
 5. The speech synthesizer according to claim 1,wherein the personalized synthesized speech model is a model foroutputting a synthesized speech, to which reading break of words utteredby the user is applied, and is an artificial neural network based modellearned by a deep learning algorithm or a machine learning algorithm. 6.The speech synthesizer according to claim 5, wherein the personalizedsynthesized speech model is a model for inferring a probability thateach word is classified as the minor probability, using text datacorresponding to the plurality of uttered words and the plurality ofunuttered words, an IP ratio of each word, and a probability of beingclassified as the minor class, which is labeled with each word.
 7. Thespeech synthesizer according to claim 6, wherein the processor transmitsthe personalized synthesized speech model to the terminal through thecommunication unit.
 8. The speech synthesizer according to claim 5,wherein, when utterance information of the unuttered words is received,the processor acquires the plurality of non-utterance IP ratios usingthe received utterance information of the unuttered words and retrainsthe personalized synthesized speech model using the plurality ofacquired unuttered IP ratios.
 9. A method of operating a speechsynthesizer using artificial intelligence, the method comprising:receiving utterance information of words uttered by a user from aterminal; acquiring a plurality of utterance intonation phrase (IP)ratios respectively corresponding to a plurality of words uttered by theuser based on the utterance information; acquiring a plurality ofnon-utterance IP ratios respectively corresponding to a plurality ofunuttered words based on the utterance information and the plurality ofutterance IP ratios, and generating a personalized synthesized speechmodel based on the plurality of utterance IP ratios and the plurality ofnon-utterance IP ratios, wherein the plurality of classes indicatingreading break of a word includes a first class corresponding to firstreading break, a second class corresponding to second reading breakgreater than the first break and a third class corresponding to thirdreading break greater than the second break, wherein a minor class has asmallest count among the first to third classes, and wherein each of theutterance IP ratios and the non-utterance IP ratios is a ratio in whicha word is classified as the minor class.
 10. The method according toclaim 9, wherein the utterance information includes reading break ofeach uttered word, a part of speech of each uttered word, and a positionof each uttered word in a sentence.
 11. The method according to claim10, wherein the acquiring the plurality of utterance IP ratios includesacquiring the utterance IP ratio of each uttered word using the numberof times that the user reads each uttered word with break correspondingto the minor class.
 12. The method according to claim 11, furthercomprising: determining a probability in which the unuttered word isclassified as the minor class, using each unuttered word, a property ofeach unuttered word, an IP ratio of an uttered word and labeling data (aprobability of being classified as the minor class), and determining aprobability of being classified as a determined IP class as anon-utterance IP ratio of the unuttered word.
 13. The method accordingto claim 9, wherein the personalized synthesized speech model is a modelfor outputting a synthesized speech, to which reading break of wordsuttered by the user is applied, and is an artificial neural networkbased model learned by a deep learning algorithm or a machine learningalgorithm.
 14. The method according to claim 13, wherein thepersonalized synthesized speech model is a model for inferring aprobability that each word is classified as the minor probability, usingtext data corresponding to the plurality of uttered words and theplurality of unuttered words, an IP ratio of each word, and aprobability of being classified as the minor class, which is labeledwith each word.
 15. A computer-readable recording medium for performinga method of operating a speech synthesizer using artificial intelligenceusing artificial intelligence, the method comprising: receivingutterance information of words uttered by a user from a terminal;acquiring a plurality of utterance intonation phrase (IP) ratiosrespectively corresponding to a plurality of words uttered by the userbased on the utterance information; acquiring a plurality ofnon-utterance IP ratios respectively corresponding to a plurality ofunuttered words based on the utterance information and the plurality ofutterance IP ratios, and generating a personalized synthesized speechmodel based on the plurality of utterance IP ratios and the plurality ofnon-utterance IP ratios, wherein the plurality of classes indicatingreading break of a word includes a first class corresponding to firstreading break, a second class corresponding to second reading breakgreater than the first break and a third class corresponding to thirdreading break greater than the second break, wherein a minor class has asmallest count among the first to third classes, and wherein each of theutterance IP ratios and the non-utterance IP ratios is a ratio in whicha word is classified as the minor class.